The embodiments described herein relate generally to tomographic imaging systems and, more particularly, to detecting objects using tomographic imaging systems.
In restricted areas such as airports and correctional facilities, detecting contraband in and/or on individuals is a high priority. Contraband such as drugs, keys, and plastic weapons may be hidden within body cavities of an individual, or on the individual (e.g., hidden under the individual's clothing). While some contraband may be detected by manually frisking passengers, privacy concerns make such methods problematic.
At least some known security scanners are capable of detecting metallic objects within body cavities and/or on an individual. However, at least some known security scanners are unable to detect non-metallic objects within body cavities and/or on an individual. While some medical imaging methods, such as X-ray computed tomography (CT) and magnetic resonance imaging (MRI), may be used to detect non-metallic objects, these imaging methods are typically quite expensive, and may involve exposing subjects to significant levels of radiation.
Low frequency electromagnetic tomography provides a safe and low cost method for imaging. Such imaging methods include electrical impedance tomography (EIT), magnetic induction tomography (MIT) and electric field tomography (EFT). However, low frequency electromagnetic tomography generally provides lower resolution and/or image quality when compared to X-ray CT and MRI. While multiple frequency electromagnetic tomography has been used to improve imaging quality, reduce artifacts, and detect abnormalities in tissue for diagnostic applications of mammography and hemorrhage detection, the low quality image resolution often limits the efficacy of such methods for detecting contraband.